The invention relates to a motor vehicle having a chassis frame and a vehicle body which are mutually connected by gluing and bolting.
Such a motor vehicle is known, for example, from German Patent document DE 34 29 839 A1, and has an upwardly open channel on its chassis frame, which channel is filled with adhesive before the joining of the chassis frame and the vehicle body. In the assembled condition of the chassis frame and the vehicle body, a vertical connecting flange at the lower end section of the vehicle body engages from above in the adhesive channel of the chassis frame. Bolted connections at the respective corners of the chassis frame and of the vehicle body, respectively, fix the two assemblies to one another, so that special chucking devices will not be necessary for the duration of the setting of the adhesive. In a further development of the known motor vehicle from German Patent document DE 37 02 619 A1, the chassis frame is shortened in its front area and is supplemented by a separate front end which has a front frame as well as a subframe.
It is an object of the invention to provide a motor vehicle with an improved further development of the chassis frame and the vehicle body, the chassis frame and the vehicle body being connected with one another in an advantageous fashion.
This and other objects are achieved by a motor vehicle having a chassis frame and a vehicle body, which are mutually connected by gluing and bolting. The chassis frame accommodates a front axle and a rear axle as well as at least one drive unit. Bolting locations are situated in the area of the front axle and the rear axle, and gluing is limited to the area or a partial area between the front and the rear bolting locations.
It is a central aspect of the invention to limit the gluing to the area, or to a partial area, between the front and the rear bolting locations. In this case, front and rear bolting locations are the locations of the bolt connection between the chassis frame and the vehicle body in the area of the front axle, on the one hand, and in the area of the rear axle, on the other hand. The bolting according to the invention in the area of the two axles creates connection locations situated close to the end section of the motor vehicle, which connection locations contribute significantly to the stiffness of the support structure of the motor vehicle composed of the chassis frame and the vehicle body. On the other hand, as a result of the large-surface gluing in the center area of the motor vehicle, a composite of the chassis frame and the vehicle body is created that has a high stiffness and strength, with advantages particularly during the introduction of force in the event of a collision of the motor vehicle, whereby the crash energy can be effectively reduced, also in the event of a lateral crash.
By means of the construction method according to the invention, a support structure for a motor vehicle is created, where, during the production process of the motor vehicle with the chassis frame and the vehicle body, first two separate assemblies will exist which permit a facilitated and cost-effective mounting, for example, in spatially separated production and mounting equipment. In this case, it is crucial that neither the chassis frame nor the vehicle body each by themselves have sufficient stiffness and/or strength for the driving operation of the motor vehicle and for the introduction of crash forces in the event of a collision of the vehicle, but that the fastening areas of the chassis frame and of the vehicle body are coordinated with one another and the type of fastening is chosen such that the assembled support structure of the chassis frame and the vehicle body as a whole meets the demanded stiffness and strength requirements. The support structure of the motor vehicle according to the invention achieved by the combination of the chassis frame and the vehicle body, in principle, is therefore a “self-supporting vehicle body” and not a vehicle body with a separation of functions of the chassis frame and the vehicle body.
The bolting preferably takes place above the area of the front and or rear axle, particularly preferably in that area of the chassis frame (and the corresponding area of the vehicle body) on which the wheel suspension supports itself at the chassis frame. In an advantageous embodiment of the invention, the bolting takes place at the upper mount of a spring-damper unit, in the following called “spring strut”, or at the upper mount of a shock absorber or a spring unit.
In a preferred further development of the invention, the bolting locations are constructed as planar areas, so that high forces can be transmitted by way of the bolted connection. If required, the bolting at each of the preferably four bolting locations (in each case, on the right and left at the front and rear axle) takes place by several bolts respectively.
In a preferred further development of the invention, areas with elongated and mutually parallel adhesive surfaces are created for producing the adhesive connection, which results in high stability under load of the adhesive connection. By means of the distance of the corresponding adhesive surfaces from the chassis frame and the vehicle body that is defined by the carried-out bolting, a defined size of the adhesive gap is achieved. As a result of the parallel formation of the adhesive surfaces, these are insensitive to component and/or mounting tolerances.
If required, the distance of the adhesive surfaces can be changed by measures in the area of the bolting locations, for example, by inserting an intermediate layer between the bolting surfaces of the chassis frame and the vehicle body or by the removal of material at the bolting surfaces.
The adhesive gap has a height of preferably at least three millimeters. When an adhesive of medium shear strength is used, an equalization of different thermal expansions of the chassis frame and the vehicle body can therefore take place as a result of the relatively large thickness of the adhesive bead in the adhesive connection.
The adhesive preferably is a single-component adhesive with a sufficiently long “open window” after the application of the adhesive and a comparatively faster hardening after the joining of the chassis frame and the vehicle body. The hardening can be accelerated by admixing a “booster”. In addition, by means of the “booster”, a hardening is achieved that is uniform along the entire cross-section of the adhesive bead and is independent of the moisture of the environment. By way of the bolting, which took place before the joining of the two adhesion partners, independently of the final hardening of the adhesive, the motor vehicle can be moved along in the production sequence and can continue to be assembled so that, in addition to contributing to the stiffness and strength of the support structure of the motor vehicle, the bolting also reduces the cycle times during the assembling since waiting time for the hardening of the adhesive is eliminated.
In a further development of the invention, the chassis frame has a right and a left side member as supporting elements in the central area, which side members can be further supplemented by a front and a rear cross member to form a rectangular supporting frame. The adhesive can advantageously be applied to the top sides of the side members and/or cross member or of the supporting frame.
If the members are present and arranged such that they form the above-described rectangular supporting frame, a very stiff supporting frame will be present which permits a surroundingly ring-shaped adhesive connection in the center area of the motor vehicle.
In a further development of the invention, the space within the rectangular supporting frame can be used for accommodating an energy accumulator, particularly an electric battery, for example, in lithium-ion technology. The composite consisting of the supporting frame at the chassis frame and of the corresponding support structure at the vehicle body is particularly stiff and capable of reducing high energies, for example, in the event of a side crash of the motor vehicle in a targeted manner and thereby protecting the energy accumulator from accident-caused damage.
In a further development of the invention, as a result of the height offset between the adhesive connection, on the one hand (along the side members and/or cross members of the supporting frame) and the bolting locations arranged in the area of the axles, preferably in the area above the axles, on the other hand, a high stiffness of the support structure of the motor vehicle is achieved in comparison to those force introductions which exercise moments on the support structure of the motor vehicle according to the invention.
In a still further development of the invention, the vehicle body is a formation closed on its underside by a floor and capable of transmitting forces introduced in the transverse direction of the motor vehicle at the level of the floor to the opposite side. In addition, the vehicle body can therefore be equipped during the production process independently of the chassis frame with interior fitting components, such as coverings of the floor, of the interior vehicle walls and of the interior of the roof, as well as with seats, a center console, instrument cluster, operating elements, etc.
In a preferred further development of the invention, the chassis frame consists of a metallic material, preferably of a light-metal material, such as an aluminum alloy. In this case, the individual components of the chassis frame can be mutually connected, for example, by welding, gluing, riveting, bolting or any other suitable joining method. The components may be made of sheet metal, extruded profiles and/or cast parts.
The vehicle body is preferably composed of components, particularly shell-shaped components, made of a plastic material. Carbon-fiber-reinforced plastics are particularly suitable for this purpose. The connection of the individual components of the vehicle body preferably takes place by gluing, for example, by use of a two-component adhesive.
For reducing the energy requirements during the manufacturing of the motor vehicle, according to a further aspect of the invention, a KTL coating and/or the application of a conventional paint coating will no longer be needed in the case of a metallic chassis frame. For achieving reproducibly loadable adhesive connections, the adhesive surfaces of the chassis frame are treated before the gluing-together, for example, cleaned by chemical methods, rendered passive, subjected to a plasma treatment, provided with a Pyrosil coating, etc. The cleaning and preparation measures mentioned in the context of the present invention are not included in the term “surface coating”.
All direction and position data in connection with components of the motor vehicle according to the invention relate in each case to the support structure of the motor vehicle composed of the chassis frame and the vehicle body and to the driving direction of the motor vehicle when driving forward.
For producing a motor vehicle according to the invention, the following production sequence is provided by way of example:
(a) producing the chassis frame of components made of an aluminum material by welding, gluing, riveting and/or bolting, in which case the components may be cast parts, extruded profiles, and/or sheet metal parts;
(b) producing the vehicle body of components made of a carbon-fiber-reinforced plastic material, preferably by gluing, in which case reinforcements made of a metallic material may be partially integrated;
(c) equipping the chassis frame with elements of the front as well as rear wheel suspension and with at least one drive unit, transmission, and/or with further components of the drive train;
(d) equipping the vehicle body with attachment parts and/or fixtures;
(e) cleaning the adhesive surfaces, particularly at the chassis frame;
(f) applying the adhesive to the adhesive surfaces, preferably to the adhesive surfaces of the chassis frame;
(g) placing the vehicle body onto the chassis frame (or vice-versa);
(h) bolting the vehicle body to the chassis frame at the bolting locations in the area above the front and the rear axle, preferably in the area of the upper mounts of the spring struts or the like;
(i) as a result of the bolted connection, a defined adhesive gap will automatically occur between the chassis frame and the vehicle body; and
(j) setting of the adhesive, in which case, because of the bolting before the conclusion of the setting, a sufficiently loadable connection of the chassis frame and the vehicle body will already exist, so that the motor vehicle will be available for further mounting volumes, surface treatments, etc. or can be conveyed for the further production sequence and/or can be driven under its own power.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.